Getting quotes from builders for 2 different extension options

[Zarara]

Hi, we’re planning an extension and the cost will dictate whether we do a single storey or 2 storey extension.
Do we therefore need to get 2 sets of drawings? Do we just need the planning drawings or will we need the building control drawings for both options. How does it work and has anybody tried to get quotes for 2 different options. The first floor extension is on top of the single storey extension if that makes a difference.

[Rhica]

We were able to get estimates off the builder before we got an architect or structural drawings done. They were also able to give us advise about the two ideas we couldn't decide between eg.if support pillars were required or if there were anything that would make it difficult such as drains, gas pipes etc